阅读说明：本技术 一种中红外锑化物量子级联激光器及其制备方法 (Intermediate infrared antimonide quantum cascade laser and preparation method thereof ) 是由 张一� 牛智川 张宇 徐应强 杨成奥 谢圣文 邵福会 尚金铭 于 2020-04-10 设计创作，主要内容包括：本公开提供了一种中红外锑化物量子级联激光器及其制备方法,包括：GaSb衬底,以及在GaSb衬底上依次外延生长的下限制层、下波导层、有源级联区、上波导层、上限制层以及上接触层；其中,有源级联区包含多个周期,每个周期包含注入区与有源区,在注入区中,电子的能量被提升至第一能级,在提升至第一能级后,电子被注入有源区,在有源区中,电子从第一能级跃迁至第二能级,并在跃迁过程中发光,第二能级低于第一能级,在跃迁至第二能级后,电子利用声子从第二能级跃迁至第三能级,第三能级低于第二能级,在跃迁至第三能级后,电子被注入下一个周期的注入区。本公开提供的中红外锑化物量子级联激光器可以覆盖整个中红外波段。(The invention provides a mid-infrared antimonide quantum cascade laser and a preparation method thereof, wherein the preparation method comprises the following steps: the optical waveguide structure comprises a GaSb substrate, and a lower limiting layer, a lower waveguide layer, an active cascade region, an upper waveguide layer, an upper limiting layer and an upper contact layer which are epitaxially grown on the GaSb substrate in sequence; the active cascade region comprises a plurality of periods, each period comprises an injection region and an active region, the energy of electrons is increased to a first energy level in the injection region, the electrons are injected into the active region after the electrons are increased to the first energy level, the electrons are transited from the first energy level to a second energy level in the active region and emit light in the transition process, the second energy level is lower than the first energy level, the electrons are transited from the second energy level to a third energy level by phonons after the electrons are transited to the second energy level, the third energy level is lower than the second energy level, and the electrons are injected into the injection region of the next period after the electrons are transited to the third energy level. The mid-infrared antimonide quantum cascade laser provided by the present disclosure can cover the entire mid-infrared band.)

1. A mid-infrared antimonide quantum cascade laser, comprising:

The optical waveguide structure comprises a GaSb substrate, and a lower limiting layer, a lower waveguide layer, an active cascade region, an upper waveguide layer, an upper limiting layer and an upper contact layer which are epitaxially grown on the GaSb substrate in sequence;

Wherein the active cascade region includes a plurality of periods, each period including an injection region in which an energy of an electron is raised to a first energy level, and an active region in which the electron is injected into the active region after being raised to the first energy level, and in which the electron is transited from the first energy level to a second energy level lower than the first energy level and emits light during the transition, and after being transited to the second energy level, the electron is transited from the second energy level to a third energy level lower than the second energy level using a phonon, and after being transited to the third energy level, the electron is injected into the injection region of a next period.

2. The mid-infrared antimonide quantum cascade laser of claim 1, wherein the materials of the lower confinement layer, the lower waveguide layer, the active cascade region, the upper waveguide layer, the upper confinement layer, and the upper contact layer comprise a material lattice-matched to GaSb, the material lattice-matched to GaSb comprising a material having a lattice constant of The material system of (1).

3. The mid-infrared antimonide quantum cascade laser as set forth in claim 1, wherein the active cascade region comprises 5-30 periods.

4. The mid-infrared antimonide quantum cascade laser as claimed in claim 1, wherein the active region is a superlattice formed by alternately growing InAs layers and AlSb layers for 3-9 times, and the thicknesses of the InAs layers and the AlSb layers in the active region are determined according to the wavelength of the mid-infrared antimonide quantum cascade laser; the injection region is a superlattice with an InAs layer and an AlSb layer alternately grown for 5-12 times, and the thicknesses of the InAs layer and the AlSb layer in the injection region are determined according to the wavelength of the mid-infrared antimonide quantum cascade laser and the thickness of the active region.

5. The mid-infrared antimonide quantum cascade laser as set forth in claim 1, wherein the material of the lower confinement layer is N-type doped aluminum gallium arsenic antimony with a composition ratio of Al _0.6-0.9GaAs_0.02-0.04Sb, the doping element is tellurium, and the doping concentration is 1e ¹⁷～1e¹⁸cm^-3The thickness of the lower limiting layer is 1-2 μm.

6. The mid-infrared antimonide quantum cascade laser as claimed in claim 1 wherein the lower waveguide layer is made of undoped Al-Ga-in-As-Sb with Al component ratio _0.1-0.3GaIn_0.2-0.4As_0.15-0.35Sb, the thickness of the lower waveguide layer is 100 nm-400 nm.

7. The mid-infrared antimonide quantum cascade laser as claimed in claim 1 wherein the upper waveguide layer is made of undoped Al-Ga-in-As-Sb with Al component ratio _0.1-0.3GaIn_0.2-0.4As_0.15-0.35Sb, and the thickness of the upper waveguide layer is 100 nm-400 nm.

8. The mid-infrared antimonide quantum cascade laser as set forth in claim 1, wherein the upper confinement layer is made of P-type doped aluminum gallium arsenic antimony with a composition ratio of Al _0.3-0.9GaAs_0.02-0.04Sb, the doping element is beryllium, and the doping concentration is 1e ¹⁸～1e¹⁹cm^-3And the thickness of the upper limiting layer is 1-2 μm.

9. The mid-infrared antimonide quantum cascade laser as claimed in claim 1, wherein the upper contact layer is made of P-type doped gallium-antimony, the doping element is beryllium, and the doping concentration is 1e ¹⁹～8e¹⁹cm^-3The thickness of the upper contact layer is 250 nm-500 nm.

10. A method for preparing the mid-infrared antimonide quantum cascade laser of any one of claims 1-9, comprising:

Sequentially epitaxially growing a lower limiting layer, a lower waveguide layer, an active cascade region, an upper waveguide layer, an upper limiting layer and an upper contact layer on the GaSb substrate; the active cascade region comprises a plurality of periods, and each period comprises an injection region and an active region;

Etching downwards from the upper contact layer until the upper surface of the upper limiting layer and the lower surface of the upper waveguide layer to form a ridge waveguide structure;

Depositing an insulating layer;

Etching the insulating layer on the ridge waveguide structure to form an electrode window;

Preparing a P-type electrode on the electrode window;

And preparing an N-type electrode on the back of the GaSb substrate.

Technical Field

The disclosure relates to the technical field of laser devices, in particular to a mid-infrared antimonide quantum cascade laser and a preparation method thereof.

Background

The mid-infrared band of 3-5 microns is a very important band, and since the absorption peaks and atmospheric windows of many gas molecules are in this band, it plays a very important role in gas detection, free space optical communication and photoelectric countermeasure.

However, the conventional quantum cascade laser emits light by radiation recombination of conduction band electrons and valence band holes, and the wavelength of the emitted light is mainly determined by the band gap of the material itself, so that it is difficult to realize wavelength adjustment in a wide range, and the entire intermediate infrared band cannot be covered.

Disclosure of Invention

The invention aims to provide a mid-infrared antimonide quantum cascade laser and a preparation method thereof, so as to realize full coverage of mid-infrared bands.

To achieve the above object, an embodiment of the present disclosure provides a mid-infrared antimonide quantum cascade laser, including:

The optical waveguide structure comprises a GaSb substrate, and a lower limiting layer, a lower waveguide layer, an active cascade region, an upper waveguide layer, an upper limiting layer and an upper contact layer which are epitaxially grown on the GaSb substrate in sequence;

Wherein the active cascade region includes a plurality of periods, each period including an injection region in which an energy of an electron is raised to a first energy level, and an active region in which the electron is injected into the active region after being raised to the first energy level, and in which the electron is transited from the first energy level to a second energy level lower than the first energy level and emits light during the transition, and after being transited to the second energy level, the electron is transited from the second energy level to a third energy level lower than the second energy level using a phonon, and after being transited to the third energy level, the electron is injected into the injection region of a next period.

The embodiment of the disclosure also provides a preparation method of the intermediate infrared antimonide quantum cascade laser, which comprises the following steps:

Sequentially epitaxially growing a lower limiting layer, a lower waveguide layer, an active cascade region, an upper waveguide layer, an upper limiting layer and an upper contact layer on the GaSb substrate; the active cascade region comprises a plurality of periods, and each period comprises an injection region and an active region;

Etching downwards from the upper contact layer until the upper surface of the upper limiting layer and the lower surface of the upper waveguide layer to form a ridge waveguide structure;

Depositing an insulating layer;

Etching the insulating layer on the ridge waveguide structure to form an electrode window;

Preparing a P-type electrode on the electrode window;

And preparing an N-type electrode on the back of the GaSb substrate.

It can be seen that the mid-infrared antimonide quantum cascade laser provided by the present disclosure only utilizes energy level transition of electrons in a conduction band to emit light, and does not need valence band holes to participate in light emission, so that wavelength adjustment in a larger range can be realized by adjusting the thickness of an InAs layer in an active cascade region, and full coverage of a mid-infrared band can be further realized, and electrons can be circularly injected into a next period from one period in the active cascade region, so that reuse of electrons is realized, thereby improving internal quantum efficiency.

Drawings

In order to more clearly illustrate the embodiments of the present disclosure or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments described in the present disclosure, and other drawings can be obtained by those skilled in the art without creative efforts.

Fig. 1 is a schematic diagram of an energy band structure of an active cascade region of a mid-infrared antimonide quantum cascade laser in an embodiment of the disclosure;

FIG. 2 is a schematic view of an epitaxial structure of a mid-infrared antimonide quantum cascade laser in an embodiment of the disclosure;

FIG. 3 is a flow chart of a method of making a mid-infrared antimonide quantum cascade laser in an embodiment of the disclosure;

Fig. 4 is a schematic process flow diagram of a mid-infrared antimonide quantum cascade laser in an embodiment of the disclosure.

Description of reference numerals:

1-a first energy level; 2-a second energy level; 3-third energy level; a 101-GaSb substrate; 102-AlGaAsSb lower limiting layer; 103-AlGaInAsSb lower waveguide layer; 104-an active cascade region; 105-an AlGaInAsSb upper waveguide layer; 106-AlGaAsSb upper limiting layer; 107-GaSb upper contact layer; 41-InAs/AlSb active region; 42-InAs/AlSb implantation area.

Detailed Description

The technical solutions of the present disclosure will be described in detail below with reference to the accompanying drawings and specific embodiments, which are understood to be illustrative only and not limiting to the scope of the present disclosure, and various equivalent modifications of the present disclosure will fall within the scope of the appended claims of the present disclosure after reading the present disclosure.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. The terminology used herein in the description of the disclosure is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure.

It will be understood that when an element is referred to as being "disposed on" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and the like as used herein are for illustrative purposes only and do not denote a unique embodiment.

With reference to fig. 1 and fig. 2, a mid-infrared antimonide quantum cascade laser provided in an embodiment of the present disclosure may include:

The optical waveguide structure comprises a GaSb substrate, and a lower limiting layer, a lower waveguide layer, an active cascade region, an upper waveguide layer, an upper limiting layer and an upper contact layer which are epitaxially grown on the GaSb substrate in sequence;

The active cascade region includes a plurality of periods, for example, may include 5 to 30 periods.

Each cycle includes an injection region in which an energy of an electron is elevated to a first energy level, the electron being injected into the active region after the electron is elevated to the first energy level, the electron transitioning from the first energy level to a second energy level in the active region, and emitting light during the transition, a light emission wavelength being determined by an energy difference between the first energy level and the second energy level, the second energy level being lower than the first energy level, the electron transitioning from the second energy level to a third energy level using a phonon after the electron transitions to the second energy level, the third energy level being lower than the second energy level, the electron being injected into the injection region of a next cycle after the electron transitions to the third energy level.

The materials of the lower limiting layer, the lower waveguide layer, the active cascade region, the upper waveguide layer, the upper limiting layer and the upper contact layer comprise materials matched with GaSb crystal lattices, and the materials matched with the GaSb crystal lattices comprise materials with the crystal lattice constant of The material system of (1). For example, InAs, AlSb, GaSb and quaternary elements thereof Or a quinary alloy.

Specifically, the active region may be a superlattice in which an InAs layer and an AlSb layer alternately grow for 3-9 times, so that the active region has a high energy level (a first energy level) and two low energy levels (a second energy level and a third energy level), and the thicknesses of the InAs layer and the AlSb layer in the active region may be determined according to the wavelength of the mid-infrared antimonide quantum cascade laser. The injection region can be a superlattice with an InAs layer and an AlSb layer alternately grown for 5-12 times, the thickness of the InAs layer and the AlSb layer in the injection region can be determined according to the wavelength of the intermediate infrared antimonide quantum cascade laser and the thickness of the active region, the superlattice with gradually changed thickness is formed, and a cascade structure is formed on the design of an energy band.

Specifically, the substrate is made of N-type doped GaSb with the thickness of about 540 μm, the doping element is tellurium, and the doping concentration is 5e ¹⁷～5e¹⁸cm^-3。

Specifically, the material of the lower limiting layer is N-type doped aluminum gallium arsenic antimony, namely Al _xGa_1-xAs_ySb_1-yThe composition ratio is smectic-matched to the GaSb substrate, e.g. the composition ratio is Al _0.6-0.9GaAs_0.02-0.04Sb, the doping element is tellurium, and the doping concentration is 1e ¹⁷～1e¹⁸cm^-3The thickness of the lower limiting layer is 1 μm to 2 μm.

Specifically, the lower waveguide layer is made of undoped AlGaInAsSb, i.e. Al _xGa_yIn_1-x-yAs_zSb_1-zThe composition ratio is smectic-matched to the GaSb substrate, e.g. the composition ratio is Al _0.1-0.3GaIn_0.2-0.4As_0.15-0.35Sb, the thickness of the lower waveguide layer is 100 nm-400 nm.

Specifically, the upper waveguide layer is made of undoped AlGaInAsSb, i.e. Al _xGa_yIn_1-x-yAs_zSb_1-zThe composition ratio is smectic-matched to the GaSb substrate, e.g. the composition ratio is Al _0.1-0.3GaIn_0.2-0.4As_0.15-0.35Sb, the thickness of the upper waveguide layer is 100 nm-400 nm.

In particular, the material of the upper confinement layer is P-type doped AlGaAsSb, i.e. Al _xGa_1-xAs_ySb_1-yThe composition ratio is smectic-matched to the GaSb substrate, e.g. the composition ratio is Al _0.3-0.9GaAs_0.02-0.04Sb, the doping element is beryllium, and the doping concentration is 1e ¹⁸～1e¹⁹cm^-3And the thickness of the upper limiting layer is 1-2 μm.

Specifically, the upper contact layer is made of P-type doped gallium-antimony, the doping element is beryllium, and the doping concentration is 1e ¹⁹～8e¹⁹cm^-3The thickness of the upper contact layer is 250 nm-500 nm.

In addition, the present disclosure also provides a method for preparing a mid-infrared antimonide quantum cascade laser, which, with reference to fig. 3, may include the following steps:

S1: sequentially epitaxially growing a lower limiting layer, a lower waveguide layer, an active cascade region, an upper waveguide layer, an upper limiting layer and an upper contact layer on the GaSb substrate; the active cascade region comprises a plurality of periods, and each period comprises an injection region and an active region.

In the injection region, an energy of an electron is raised to a first energy level, the electron is injected into the active region after being raised to the first energy level, the electron is transited from the first energy level to a second energy level in the active region, and emits light during transition, the second energy level is lower than the first energy level, the electron is transited from the second energy level to a third energy level by a phonon after being transited to the second energy level, the third energy level is lower than the second energy level, and the electron is injected into an injection region of a next cycle after being transited to the third energy level.

S2: and etching downwards from the upper contact layer until the upper surface of the upper limiting layer and the lower surface of the upper waveguide layer to form a ridge waveguide structure.

Wherein, S2 may include the following sub-steps:

S21: and spin-coating photoresist on the upper contact layer, and using a photoetching plate as a mask by using a common contact exposure method to prepare a mask pattern of the ridge waveguide, wherein the whole pattern is positioned on the upper surface of the device.

S22: and etching the upper surface by using the photoresist as a mask so as to obtain the ridge waveguide structure.

Specifically, the etching may be performed by an Inductively Coupled Plasma (ICP) method, and may also be performed by a Reactive Ion Etching (RIE) method, which is not limited in this disclosure. The ridge waveguide structure formed by etching can be a single-structure strip waveguide structure or a double-channel ridge waveguide structure, for the single-structure strip waveguide structure, the ridge can be a wide strip and has a width of about 100-200 μm, and for the double-channel ridge waveguide structure, the ridge can be a narrow strip and has a width of about 5-35 μm.

S3: and depositing an insulating layer.

Specifically, a Plasma Enhanced Chemical Vapor Deposition (PECVD) process can be used to deposit SiO with a thickness of 250nm ₂Or SiN _xAs an insulating layer.

S4: and etching the insulating layer on the ridge waveguide structure to form an electrode window.

Specifically, contact lithography can be used, a photolithography mask is used as a mask above the ridge waveguide structure to prepare an electrode window pattern above the ridge waveguide structure, and then photoresist is used as a mask to etch SiO with the thickness of 250nm by ICP (inductively coupled plasma) ₂And the insulating layer enables the upper contact layer to be exposed for forming ohmic contact with the metal electrode.

S5: and preparing a P-type electrode on the electrode window.

Specifically, Ti or Pu or Au may be sputtered at the electrode window using a magnetron sputtering method, and the thickness may be 20nm, or 50nm, or 300nm, to form an ohmic contact of the P-face.

S6: and preparing an N-type electrode on the back of the GaSb substrate.

Specifically, the lower surface of the substrate is thinned and polished to thin the substrate to 150-200 um, then an N-type electrode is made of Ni, AuGe or Au material, the thickness of the N-type electrode can be 5nm, 100nm or 300nm, and finally the N-type electrode is placed into rapid thermal annealing (RTP) equipment for annealing to form N-surface ohmic contact.

As shown in fig. 4, the method may further include:

S7: cleaving the epitaxial wafer into strips, coating the cavity surface of the device, and coating lambda/4 Al on the front cavity surface by electron beam evaporation equipment ₂O₃And back cavity surface is evaporated with 200nm Al ₂O₃And 100nm Au, preparing a device cleavage groove, and performing the processes of cleavage, sintering, reverse welding and the like on the device, which are not the key points of the invention and are not described herein again.

In summary, it can be seen that the quantum cascade laser provided by the present disclosure is based on antimonide and related materials thereof, and is different from the existing quantum cascade laser in material, and due to differences in properties such as strain, forbidden bandwidth, thermal conductivity, and refractive index of different materials, the quantum cascade laser of the antimonide provided by the present disclosure is specially designed in terms of various parameters such as energy band structure, thermal conductivity, resistivity, and refractive index, and especially, the design of the energy band structure and the device overall structure is greatly different from the existing quantum cascade laser, so that the full coverage of the mid-infrared band is achieved, and the defects in the prior art are overcome.

The above embodiments in the present specification are all described in a progressive manner, and the same and similar parts among the embodiments may be referred to each other, and each embodiment is described with emphasis on being different from other embodiments.

The above description is only a few embodiments of the present disclosure, and although the embodiments of the present disclosure are as described above, the above description is only for the convenience of understanding the technical solutions of the present disclosure, and is not intended to limit the present disclosure. It will be understood by those skilled in the art of the present disclosure that various changes in form and details may be made therein without departing from the spirit and scope of the disclosure, and that the scope of the disclosure is to be limited only by the terms of the appended claims.